Run results for: for vs. for-of vs. reduce (array to ID-keyed object)

Run details:

User agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:97.0) Gecko/20100101 Firefox/97.0

Browser: Firefox 97

Operating system: Windows 7

Device Platform: Desktop

Date tested: 2 years ago

Script Preparation code:

var itemCount = 1000
var items = new Array(itemCount)

for (var i = itemCount - 1; i >= 0; i--) {
  items[i] = { id: i, data: 920501 }
}

Tests:

for loop
const itemsById = {} for (let i = items.length - 1; i >= 0; i--) { itemsById[items[i].id] = items[i] }
for-of loop
const itemsById = {} for (const item of items) { itemsById[item.id] = item }
reduce
const itemsById = items.reduce((result, item) => { return { ...result, [item.id]: item } }, {})